This invention relates to a method of making a cross joint between different size pipes. This method is applicable to a manufacturing process of an ordinary fuel delivery rail which is utilized for an automotive engine equipped with a fuel injection system. This method can be also applied to miscellaneous manufacturing processes for joining a large pipe and a small pipe perpendicularly.
In a conventional fuel delivery rail, a plurality of sockets for receiving respective fuel injectors are interconnected by connecting pipes (see FIG. 11). Each socket is formed in a tubular member having a larger diameter than that of the connecting pipe. Therefore, it is indispensable to make a cross joint between the pipes. As it is well known, it causes several manufacturing problems to make a cross joint between different size pipes. To a wall segment of a large pipe, an aperture of a complicated form should be drilled or machined. On the other hand, to an end of a small pipe, a complicated edge should be formed coincident with the aperture. Nevertheless, a gap is produced in the joint and it causes fuel leakage therefrom.
U.S. Pat. No. 3,971,500 (Kushner et al.) discloses a method of metallurgically joining tubing to a wall segment. In this method, a circumferentially arranged lip means is provided with a small pipe which is inserted into an aperture formed in a wall segment of a large pipe. However, this type of lip means in a form of a ring bead has a disadvantage that it allows the small pipe itself to rotate around the position. This rotation tends to produce a misalignment between the pipes and makes it difficult to keep a precise angular orientation relative to the corresponding fuel injector.
Furthermore, since the edge of the small pipe is cut down at right angles, a portion of the edge protrudes into the inside circle of the large pipe. This portion obstructs the fuel injection flow from a socket to a fuel injector if it is applied to a fuel delivery rail. To make matters worse, this protrusion tends to damage the enclosed parts within the socket, such as a fuel filter element or seal members.